A United Nations report raised the threat of climate change to a whole new level on Monday, warning of sweeping consequences to life and livelihood. The report from the UN’s intergovernmental panel on climate change concluded that climate change was already having effects in real time – melting sea ice and thawing permafrost in the Arctic, killing off coral reefs in the oceans, and leading to heat waves, heavy rains and mega-disasters. And the worst was yet to come. Climate change posed a threat to global food stocks, and to human security, the blockbuster report said.

The warning signs about climate change and extreme weather events have been accumulating over time. But this report struck out on relatively new ground by drawing a clear line connecting climate change to food scarcity, and conflict. The report said climate change had already cut into the global food supply. Global crop yields were beginning to decline – especially for wheat – raising doubts as to whether production could keep up with population growth. “It has now become evident in some parts of the world that the green revolution has reached a plateau,” Pachauri said. The future looks even more grim. Under some scenarios, climate change could lead to dramatic drops in global wheat production as well as reductions in maize. “Climate change is acting as a brake. We need yields to grow to meet growing demand, but already climate change is slowing those yields,” said Michael Oppenheimer, a Princeton professor and an author of the report.